BANGKOK – The US-trained Royal Thai Navy on Saturday (December 20) geared up to stop all Thai ships in the Gulf of Thailand transporting fuel and military supplies to Cambodia, the first major use of the artillery-firing navy in the five-month-long border war.

The US Seventh Fleet uses the Gulf of Thailand when its aircraft carriers and other vessels dock near Bangkok at Sattahip port where Thailand’s First Naval Area Command is based to secure the gulf, which is peppered with inhabited Thai and Cambodian islands, navy facilities and oil rigs.

In addition to intercepting Thai ships, including fishing and commercial vessels, the navy said it would stop Thai-owned ships sailing under foreign flags and registrations, if they are suspected of transporting fuel, weapons, ammunition or other military equipment across the gulf to reach Cambodia’s south coast.

Thai shipping companies facilitating their travel, vessels’ owners, suppliers, chandlers and others linked to Thai ships violating the ban would also be held responsible, officials said.

The navy warned shippers about “high-risk zones” in the Gulf of Thailand’s northeast waters, close to southern Cambodia’s beach towns and scattered ports. That coastline is rife with smugglers, human traffickers, fugitives and others illegally using small boats to avoid crossing the nearby Thailand-Cambodian land border.

Thai news reports claim Cambodia has deployed drones to buzz and potentially disrupt or bomb oil platforms in the gulf, including those operated by state-run PTTEP. An industry source told Asia Times that Chevron’s platforms have also reported drone activity over their assets. Reports said the Thai navy has deployed helicopters and ships to protect the platforms.

“The declaration of a high-risk zone is neither a blockade nor a closure of the Gulf,” Navy spokesman Captain Nara Khunthothom said.

“This operation concerns a bilateral conflict between Thailand and Cambodia, and our actions must not impact third countries. We will take all necessary steps to cut off these supplies,” Nara said.

“This is a peaceful approach to restrict Cambodia’s ability to act against Thailand,” Defense Minister General Nattaphon Narkphanich told reporters.

In addition to cargo vessels, passenger ferries and other ships, more than 10,000 fishing boats trawl the Gulf of Thailand’s shallow waters, Nattaphon said.

The National Security Council endorsed the Thai Maritime Enforcement Command Center (Thai-MECC) to be in charge of stopping the ships. The intercepts include maritime surveillance of cargo including transfers while at sea, plus loading and unloading on land, Thai-MECC spokesman Navy Admiral Jumbol Nakbua said.

Thai geeks, sleuths, shipping experts, military researchers and others have already started tracking suspicious ships in the gulf, and posting their evidence online. Many of them use MarineTraffic.com to determine ships’ locations.

They posted information about a Thai-flagged vessel which allegedly sailed to Singapore to collect fuel on December 10, and then docked and unloaded it at a Cambodian port on December 14.

Several other vessels they tracked had departed from Thailand’s Laem Chabang Port, near Bangkok, allegedly carrying fuel to Cambodia. A handful of Thai shipping companies have legally been sending fuel to Cambodia for years.

The Gulf of Thailand is bigger than the Persian Gulf, covering a surface the size of Poland. The 123,000-square-mile (123,550-square kilometer.) gulf forms a cul-de-sac in the western Pacific, bordered by Thailand, Cambodia, Vietnam and Malaysia. Thailand shares the Gulf of Thailand with Cambodia.

The navy’s interceptions may become hampered by Thai and Cambodian maps of the gulf, which outline their disputed, overlapping maritime borders around prized undersea natural gas and petroleum zones, and drilling rigs operated by Chevron and other foreign and Thai corporations.

Cambodia’s share of the Gulf of Thailand includes nearby Ream Naval Base next to sheltered Sihanoukville Bay.

Washington fears if a US-China war erupts, Ream Naval Base will be used by Cambodia’s close ally China, which has financed and constructed the base’s newest facilities and recent extensive dredging, allowing deep-water vessels including warships to dock, load and unload, and undergo maintenance and repairs.

China’s privileged access to the facility would potentially provide it a strategic southern flank it has until now lacked in any conflict in the South China Sea.

Cambodia, which has recently improved US relations after a downturn in ties saw the two sides cancel their regular Angkor Sentinel joint exercises in 2017, insists Ream will remain open to all international shipping.

US President Donald Trump met Cambodian Prime Minister Hun Manet at the ASEAN summit in late October, where the two leaders agreed to resume the Angkor Sentinel drills in 2026. The US also agreed to lift an embargo on arms sales to Cambodia.

At the same summit, Trump oversaw a ceasefire announcement between the two sides. US statements since the resumption of hostilities have been perceived in Bangkok as favoring Cambodia’s version of events over Thailand’s allegations of new landmine laying that killed and injured Thai soldiers and restoked the hostilities.      

The geopolitics of the conflict are as foggy as those charges and allegations. Thailand’s army recently displayed Chinese-made anti-tank missiles that it seized when Cambodian troops retreated from Hill 500 in Thailand’s Ubon Ratchathani province.

Beijing said its “normal defense cooperation” with both Bangkok and Phnom Penh had nothing to do with the border clashes. China sells weapons to both Thailand and Cambodia.

However, China has supplied Cambodia with the PHL-03 long-range rocket system, which Beijing has transferred to only a handful of countries worldwide and can hit targets 130 kilometers away. Cambodia’s use of the weapon would mark a grave escalation, extending the conflict beyond border provinces and putting major provincial cities at risk.

“China has been working actively for de-escalation,” China’s foreign ministry said on December 18.

The US is a non-NATO treaty ally with Thailand and conducts several annual military training exercises with Thailand’s armed forces, including its navy in the Gulf of Thailand and Andaman Sea.

The Thai navy’s main force includes frigates brandishing 127mm guns and corvettes for coastal patrols and attacks with Bofors 40mm guns. It also has one aircraft carrier armed with a 20mm Gatling gun. 

The flat-topped vessel is mostly used for helicopters and humanitarian crises such as providing an emergency hospital or flood relief. The Thai navy is also trained during annual US-led military exercises, including Cobra Gold and other multinational drills.

For example, the US-led CARAT (Cooperation Afloat Readiness and Training) exercise focuses on naval partners in Southeast Asia, including Thailand. CARAT upgrades navies’ skills in surface water warfare, diving and salvage, armed patrols and piloting navy aircraft. Another US-led exercise, SEACAT (Southeast Asia Cooperation and Training), also concentrates on maritime security.

China’s most prominent naval exercises with Thailand include much smaller Blue Strike bilateral drills with China’s Marine Corps, Thai Navy Marine Corps and special warfare units. They have practiced amphibious assaults, anti-terrorism strategies, island seizure and other maritime confrontations.

China and Thailand are stuck in a long-running saga over plans for Beijing to supply Thailand with as many as three submarines. The deal has stalled on various fronts, but has nonetheless raised US concerns over the access China could gain to key naval facilities American forces use in Thailand.

Fighting between the two Buddhist-majority nations has, since July, has involved mostly Thai air and mutual artillery attacks along their disputed frontier. Clashes along the curved 500-mile-long Thailand-Cambodian frontier continued on Saturday (December 20).

Last week, Thailand’s US-supplied F-16 warplanes bombed the Ghost Mountains in northern Cambodia’s Preah Vihear province, and the outskirts of Poipet town in western Banteay Meanchy province, Cambodia’s defense ministry said. Thailand has also aerially bombarded alleged scam center facilities housed in casino complexes in Poipet.

“Hundreds of [Cambodian] BM-21 rockets were fired, not at soldiers, but at farmland and civilian areas,” Thai army spokesman Colonel Richa Suksuwanon said on December 18. “This is not right, and we will surely retaliate,” Richa said.

At least 50 people, including 21 troops and 12 Cambodian civilians, have been killed – plus half-a-million people displaced – on both sides of the Thailand-Cambodian border war. Thailand holds 18 Cambodian prisoners of war. Cambodia has blocked Thais trying to return to Thailand across the border.

The conflict is concentrated along frontier territory claimed by both nations, causing havoc in Thailand’s modernizing northeast border provinces of Surin, Buriram, Sisaket, Ubon Ratchathani, Chanthaburi, Sa Kaeo and Trat.

On the opposite side, Cambodia’s much less developed provinces hit by assaults during recent clashes include Preah Vihear, Banteay Meanchey, Battambang, Pursat, Koh Kong and the northern edge of Siem Reap province, home to the world-renowned Angkor ruins.

Richard S Ehrlich is a Bangkok-based American foreign correspondent reporting from Asia since 1978, and winner of Columbia University’s Foreign Correspondents’ Award. Excerpts from his two new nonfiction books, “Rituals. Killers. Wars. & Sex. — Tibet, India, Nepal, Laos, Vietnam, Afghanistan, Sri Lanka & New York” and “Apocalyptic Tribes, Smugglers & Freaks” are available here